Electrolysis technology is increasingly being adopted as a method of generating hydrogen and oxygen where there is a demand for hydrogen/oxygen fuel for combustion or hydrogen fuel cells. One driving force behind this trend is a shift away from fossil fuels as an energy source.
The main types of electrolysis involve alkaline solutions and proton-exchange membranes. While both are proven technologies, they have limited conversion efficiency (i.e. the energy produced versus the energy input to drive the process) of less than 90%. Additionally, there is an initial high capital cost so applications generally are limited to specialist purposes.
A technical paper by Mizuno et. al., entitled “Confirmation of anomalous hydrogen generation by plasma electrolysis” in 4th Meeting of Japan CF Research Society 2003, Iwate, Japan: Iwate University, discusses hydrogen generation in quantities greater than Faraday's Law predicts.
Specifically, Mizuno teaches that plasma forms when an applied potential difference between electrodes exceeds 100V in an aqueous solution and that a mixture of oxygen, hydrogen and steam are formed on the surface of a cathode.
However, Mizuno states:
“The generation of hydrogen at levels exceeding Faraday's law is observed when the conditions such as the temperature, current density, input voltage and electrode surface are suitable. The precise conditions are still not known, and controlling these conditions is difficult, so only a few observation of excess hydrogen have been made.”
Mizuno observes non-Faradic hydrogen generation, for example, when plasma electrolysis occurred at 2 A/cm2 of input current at 120V and at an electrolyte temperature of 80° C. Mizuno finally concludes that non-Faradic hydrogen generation occurs when the potential difference between electrodes is several hundred volts, but does not provide any explanation for controlling the plasma beyond short bursts.
A theory explaining plasma electrolysis that produces non-Faradic quantities of hydrogen is outlined in a technical paper by Cirillo et. al., entitled “Transmutation of metal at low energy in a confined plasma in water”, in Eleventh International Nuclear Conference on Condensed Matter Nuclear Science, 2004, Marseille, France.
Specifically, Cirillo teaches that electrolysis is aided by metal anions, dissolved in an electrolyte, which form a screen spaced a few nanometers from the cathode, thereby effectively forming an anode. This is known as a double layer.
Under conventional electrolysis conditions, hydrogen gas is generated at the cathode with much of the space between the cathode and the anion screen being filled with H3O+ and H2. Ions of hydrogen migrate through the screen to discharge on the cathode and produce hydrogen gas.
Increasing the applied voltage above 80V has the effect of significantly increasing hydrogen gas production to the point that the space between the cathode and the anion screen becomes filled with hydrogen gas. The gas has a much lower conductivity than liquid electrolyte, so the resistance increases until unstable bursts of plasma form to discharge the potential difference between the cathode and the anion screen. The high localised voltage can result in cathode temperatures, for tungsten electrodes, greater than 3000° C. Such heating of the cathode results in instant vaporization of electrolyte from the surface of the cathode and destabilizes plasma formation.
Cirillo does not discuss hydrogen generation as a goal and does not address problems of stabilizing plasma.